Thermal convection in a relatively “thick” horizontal cylindrical layer with isothermal boundaries, uniformly rotating around a horizontal axis, is experimentally investigated. The inner boundary of the layer has a higher temperature—the liquid is stably stratified in a centrifugal force field. The subject of the study is the oscillations of a non-isothermal liquid in the cavity frame and the averaged convective flows excited by these oscillations—“vibrational” thermal convection. In the case under consideration, the oscillations of non-isothermal fluid in the cavity are excited by the gravity field and have a tidal nature. The excitation threshold of averaged convection is determined by the vibration parameter and the centrifugal Rayleigh number. The experimental findings align with the theoretical calculations, which are derived from the equations of vibrational thermal convection, obtained by the averaging method. A new mode of thermal convection, which consists of the excitation of intense parametric oscillations of a non-isothermal liquid in the cavity, has been discovered in the experiments. Under certain conditions, parametric instability manifests itself up to the excitation of vibrational thermal convection. Parametric instability has a threshold character and manifests itself in the form of an azimuthally periodic system of consistently rotating longitudinal two-dimensional rolls. The system oscillates at a frequency that is half of the rotation frequency, the frequency of the centrifugal force field modulation. To the best of the authors' knowledge, the excitation of parametric oscillations in a rotating non-isothermal fluid has been discovered for the first time. The conditions for parametric convective instability excitation have been thoroughly examined, and dimensionless control parameters have been delineated. Furthermore, a comprehensive map of stability and various convective regimes has been constructed. The study has demonstrated the significance of parametric oscillations in the context of averaged convective flows and heat transfer.
Vjatkin et al. (Thu,) studied this question.